1. Field of the Invention
This invention relates to the treatment of corn hulls and similar materials. More particularly, this invention relates to the treatment of corn hulls and similar materials to obtain two fractions therefrom comprising a holocellulose fraction and a non-carbohydrate fraction.
2. Description of the Prior Art
Many processes are known in the art for obtaining various fractions from plant materials. For example, wood chips may be treated to obtain cellulose having varying degrees of purity. Typically, wood pulping processes involve treatments at high temperatures under highly alkaline or acid conditions and may include the use of certain chlorine and sulfur compounds to assist in the solubilization of lignin. The liquor resulting from such treatments may comprise mixtures of lignins, hemicellulose, various sugars and degradation products. Efforts have been made to recover various components of the liquor but such have not proven entirely satisfactory due, principally, to the large amounts of degradation products present.
One approach which has been taken to minimize the formation of degradation products is the utilization of alcohols for removal of lignins in the pulping process. U.S. Pat. Nos. 1,856,567 to Kleinert et al. and 2,037,001 to Aronovsky disclose various procedures for the alcoholic extraction of wood pulp. U.S. Pat. No. 2,166,540 to Bailey teaches the treatment of lignified cellulosic material with an aqueous alkaline solution of alcohol. Pulping using aqueous ethanol at high temperatures is described by T. N. Kleinert in Tappi, Vol. 57, No. 8, August 1974.
There are a number of procedures disclosed in the art directed to the extraction of hemicellulose from fibrous waste products such as corn hulls, cotton seed hulls, oat hulls and the like utilizing aqueous alkali. Exemplary of such procedures are those disclosed in U.S. Pat. Nos. 1,819,233 to Darling; 2,218,567 to White; 2,709,699 to Wolf et al.; 2,801,955 to Rutenberg et al.; 2,868,778 to Watson et al.; and 3,879,373 to Gerrish et al. These procedures generally suffer the disadvantage of producing a colored, impure, hemicellulose product. German Offenlegungsschrift Nos. 2,358,472 and 2,365,457 disclose processes for treating oat hulls to recover xylose, cellulose and lignin.
U.S. Pat. No. 3,716,526 to Schweiger teaches a method for producing a relatively pure hemicellulose product whereby corn hulls are first subjected to an alkaline extraction procedure to produce a crude hemicellulose product and then treating such product with an aqueous organic-acid containing liquid to solubilize the impurities.